I felt bad for Georgi being overshadowed by Viktor even on his birthday so I drew a thing.
I mean, before Magnus realized Alec wasn't out, he hit on him pretty hard and obvious for everyone around. But (speaking from personal experience) being closeted, doesn't necessarily equal having no experience at all, so I'm not surprised Magnus didn't assume, Alec never had a relationship. I think a lot of us dated or were intimate with ppl in secret before coming out, it's not uncommon at all. Like Magnus said, Shadowhunters are a don't ask/don't tell culture, and even offered to date secretly